Schaffer
gyroscopic apparatus



Aug. 16, 1966 M. A. SCHAFFER 3266325 GYROSCOPIC APPARATUS Fled Feb. 26,1965 4 Sheets-Sheet 1 F'iled Feb. 26, 1965 M. A. SCHAFFER GYROSCOPICAPPARATUS 4 Sheets-Sheet 5 INVENTOR. MAX 1, SCHAFFER Aug. 16, 1966 M. A.SCHAFFER GYROSCOPIG APPARATUS Filed Feb. 26, 1965 4 Sheets-Sheet 4 F lG. 5.

INVENTOR. MAX 4. SCHAFFER Unted States Patent G 3266,325 GYROSCOPCPPARATUS Max A. Schaler, Williston Park, N.Y. assignor to Sperry RandCorporation, Great Neck, N.Y., a corporation of Delaware Filed Feb. 26,1963, Ser. No. 261,005 I1 Claims. (Cl. 745.34)

Thiis invention relates to gyroscopic apparatws and particulanly to thetype known as gyroscopic stable platforms.

The requirement fo1 increasecl navigational accuracy, particularly formilitary aircraft and missiles, h-as bro.ught about the developrnent ofvery accurate inertial stable platforms. Presently, very accurate stableplatforms of this type -utilize floated inerfiial elements. Floatedinertialelementsare extremely expensive, d-ifiieult to marmfacture, andhave in turn introdnced new mai-ntenance and reliaxbility prciblems.Fturther, due to the fact that the inertial elements are lloated, theflotation fluid must be contnually maintained within a predeterminedtemperature range for proper operation, and if not m-aintained withinth=is temperature range, the initial warmup time is prohibitivepartioulanly for certain military applications. Another disadvantage ofthe prior art inertial stable plattorms is that they are ur1d:uly large,heavy and complex.

It is thereiore a primairy object of the present inwention to provide agyroscopic stable reference apparatus that is accurate, reliable andrelatively easy to maintain.

It is a urther object of the present invention to provide a gyroscopicstable reference apparatus which utilizes non-floated inertial elementsthereby eliminating the pro lerns associated with flotation wlmileproviding substantially the same accuracy.

It is another obect of the present invention to provide an accurate andreliaxble gyroscopic sta1ble reference apparatus that is small in size,light in weight, and relati=vely easy to rnannfactxure and maintain.

The albve and other objects are accomplished by means of the presentinvemion which in a preferred enubodiment utilizes a two degree offreedorn ver-tieal gyroscope and a single degree of freedom gyroscopemounted with in a oommon pitch stabilized gimbal. The pitch stallJillZfdgirrnbal in turn is pivotably mounted within a roll stabilized gimbalthat is piv0tably mounted for ro=tation about the roll axis of thecraft. In the preferred emlrodiment, the single -degree o.f freedomgyroseope is mounted on an azimuth stabilized element that is pivotablyrotated on said pitch gi1nrbal thereby providing a virtna=l seoonddegree of fireedom to the single degree of freedom gyroscope in orderthat it provides directional gyroscope information, First and secondacceleration responsive devices are mounted on the azimuth stabilzedelement to provide signal representative of the tilt of said element tostabilize the roll and pitch gimbals. By utilizing the principlesdesoribed in U.S. Patent 2,97 0,480 in conjunction With the preferredembodiment described brefly albove, aceur-acy equivalent te inertialgyro perormance has been attained without flotation of the gyro.Further, utilizing a large anna1lar hearing provides access through thehearing opening to the components of the stable reference apparatus forcase of maintenance. Ihis feature also permitis the apparatus to be mademore compact since the opening in the annular hearing is made largeenough to penm-t a portion of the sta=ble reference apparatus to swingthrough the opening da1ring operation. The staxble reference apparatushas been made more compact in anotlrer direction by mounting thevertical gymscope with its pitch gimbal journalled inboard rather thanouthoard.

Referring to the drawings,

FIG. 1 is a schematic perspective of a gyroscopic stable 3,266325Patented August 16, 1966 refierence apparatus constnucted in accordancewith the present invention,

FIG. 2 is an elevation view partly in section of an actual gyroscopicstable reference atppar-atus utilizin-g 1wo gyroscopes,

-FIG. 3 is a bottom view of the apparatus of. FIG. 2;

FIG. 4 is a sectional view taken along lines 44 of FIG. 2; and

FIG. 5 is a sectional view taken along lines 55 of FIG. 4.

Referring to the drawin gs, and particularly FIG. 1, a gyro stablep-latfonm I is mounted -fo=r movement within a housing 2 that is fixedwith respect to an airirame 3, for example. The enter roll ginrbal 4 oithe stable platform 1 is mounted topivot around an axis 5 that iscoincident with the foreand-arft axis of the aircraft about which theaircraft rolls.- The outer roll gimbal 4 is mounted to pivot anound theaxis 5 by means of large spaced annular beanings 10 and 11, shown inF168. 2 and 3 in order to simplify FIG. 1, which have ther innel races12 and 13 oonnected to respectiVe extremities of the outer roll ginrba-l4. The respect-ive orter races 15 and 16 of the spaced bearings 10 and11 are mounted within the hollsi-ng 2 by means of respectivecircurnferentially spaced shock morunts 17 and 18. The large rollbearings 10 and 11 permit full freedom in pitch while maintaining aminimum dimension in the direction of the axis 5 in a manner to be morefully explained. An outer pitch girnbal 20 of the stable platform 1 isrotatably mounted on the enter roll gi1nbal 4 by means of spacedtrunnions 21 and 22 to pivot about an axis 213 that is perpenclicula1 tothe axis 5. The axis 23 is nonmally parallel vvith the atlrwartship axisof the cratt about which the crait pitclres A two degree 0f freedomvertica-l gyroscope 24 has its onter ginnbal 25 rotatably mounted to--pivot on the oute1 pitch gimbal 20 by means ofspaced tr.urinicns 26 and27 around an axis 28- that is parallel to the axis 23. "I0 conservespace, the trunnions 26 and 27 are disposed in board of the girrnbal 25.The inner gimibal 29 of the vertical gyroscope 24 is in turn rotataablymounted upon the outer gimbal 25 to pivot arbou-t an axis 30 that isnormally parallel to the axis 5 by means of spaced tnun nions 31 and 32.The vertieal :gy ro 24 has a rotor 33 Wlrich spins about a normal-lyVer-tical axis 34 Within the gimbal 29.

To provide azirnuthal reierenee inormation, a second gyroscope 3 5havingdirectioral characteristics is mounted on a portion of the outerpitch gim bal 20 extending on the other side of the axis 23. Preferalblythe second gyroscope 35 is a single degree of -freedom gyroscope mountedon a platform 36 that is journalled on the outer pitch girnbal 20.bymeans Off spaced trunnions 37 and 38. The platform 36 is stabilized inazimuth in a man'ner to be explained albout an axis 40 that is normallycoincident with or parallel to the axis 34. By mounting the gyroscope 35on the platform 36 which is also stabilized in pitch and roll in amarmer to be explained, the gymscope 3*5 may be a single degree Olffreedom type whi ch by virtue of its disposition provides azirnuthalinformation comparable to a two degree of freedbrn direetionalgyroscope. An aoceleration responsive device in. the nforrn of a liquidlevel 41 that is responsive to accelerations in the northsouth directionand to til-t of the platform 36 is also mounted on the platform 36.Another similar liquid level 42 is mounted on the platform 36 to laeresponsive to accelerations in the east-west d-irection and to tilt.

It-Will be appreciated that a two degree of freedorn directionalgyroscope may be directly mounted on the outer pitch gim-bal 20 in lieuof the single degree of freedorn o f gyroscope 35 mounted on theplt1form 36 to provide an azimuth reference. In that event, the lquidlevels 41 and 42 may be mounted on the vertical gimbal of the two degreeof lfreedom directional gyrosoope to be responsive to tilt andaocelerations in the nort-h-south and eastwest direetions respeetively.With the errrbodiment shown in FIG. 1, it is not necessary to use a twodegree of reedom directional gyroscope since the single degree offreedom gyroscope 35 mounted as shown in stabilized roll and pitchgimbals 4 and 20 respectively maintains the outer pitch gmbal 20vertical even during maneuvers, thus permitting the use ot a low dritlrtsingle degree of freedom gyro 35 in lieu of a more expensive and complextwo degree Olf afreedom gyro.

The operation of the system will be described with regard to a slavedgyro mode Otf azimuth operation in which a flux valve 43 provides anelectrical signal representative ocE the magnetic heading of the craft.The flux valve 43 is connected to a control transformer 44 and providesthe electrical heading signal to the stator thereof while the rot-or ofthe control transtormer 44 is connected to an azimuth servo shatft 45f-or rotation therewith. An electrical signal representative of thedifierence between the relative positions of the rotor and stator of thecontrol trans-former 44 is amplified in an amplifier 46, demodulated ina deanodulator 47 and then transmitted to the torquer portion orf acornloined pick-off and torquer 50 of the azirnuth gyro 35. Thecom=bined pick-off and torquer 50 may be ozf the type shown in U.S.application Ser. No. 32,780, entitled Electronragnetic TransducerDevice, invented lny Robert H. Bolton, filed on May 3 1, 1960, andissued May 7, 1963 as U.S. Patent No. 3,089,044. A correction signalrepresentative out the earths rate is connected to one input terminal ofthe algebraic summing amplifier 46 in order to correct for the eiects ofthe earths rotational rate on the gyroscope 35. The gyroscope 35precesses in azirnuth in response to the torquing acton orf the pick-ofiand torquer 50. The precession provides a signal trom a controltransformer 4 which is responsive to the azimuthal position of theplatfonm 36. The signal from the control transformer 54 is -amplified inan amplifier 55 and energizes a servomotor 57 to drive the azi muthservo shaft 45 through a gear train 58 to a position which causes thesignal from the control transformer 44 to go to zero. The slaved azimuthgyro system there- Ifore operates in a manner similar to that describedin U.S. Patent 2,808,656, entitled Gyromagnetic Reference Sys tems,issued to A. D. Perone on October 8, 1957.

Rotation of the azimuth servo shaft 45 also causes rotation o the rotorportion orf a resolver 60 andthe rotor of a synchro transmit-ter 61which are both connected thereto. The resolver 60 may le of the typedisclosed in U.S. Patent 2591697, of Hays, entitled Stable R6I- erenceApparatus, issued April 8, 1952. A synchro transmit-ter 6-1 is connectedto provide an azimuthal signal to the control transformer 54 and alsomay Ibeconnected to transrnit heading signals to the aircraft control orweapons systems. A synchro transmitter 62 may also have its rotorpositioned in accordahce With the azimut-hal position of the platform 36while its stator is mounted on the pitch gimbal 20 in order that itsstator provides an azimuthal signal to the aircralft control or weaponssystems. The slaved azirnuth gyro s'ystem therexfore' operates in amanner similar to that described in said U.S. Patent 2808,65 6. The spinaxis of the azirnuth gyro 35 is maintained level Dy means oi the signa1from the pick-ofi portion of the pick-o torquer 50 Which is amplified inan amplifier 51 before it is connected to energize a torque motor 53.The action of the torque motor 53 tending to rotate the platform 36 inazimuth causes the spin axis of the azmuth gyro 35 to return to a levelc0ndition thereby eliminating the pick-o signal.

The vertial gyro 24 has a pick-oi 65 associated with its outer gimbal 25whioh provides a signal representatiwe of the pitch 06 the aircraft to apitch torque motor 66 mounted to drive the pitch gmbal 20 in order tomaintain it vertical, i.e. stabilized in spite of maneuvers orf the 4crasft or tilt. A roll piek-ofi 67 associated with the gimbal 29provides a signa.l representative o the roll of the crarft to a rolltorque motor 68 mounted to drive the roll gimbal 4 to maintain ithorizontal or stabilized in spite of maneuvers of the crat.

A liquid level 4-1 is mounted on the platform 36 in order that it willsense horizontal acceleratons, dor example, in the east-west directionand tilt of the platform about a north-south axis. The signal from theliquid level 41 is amplified in an amplifier 70 and applied to one inputterminal of the resolver 60. The liquid level 42 is oriented on theplatform 36 in order that it Will sense horizontal accelerations in anorth-south direction and tilt of the plattorrn 36 about an cast-westaxis. The liquid level 42 is connected to an input terminal of a summingamplifier 71 whioh in turn is connected to another input terminal of theresolver 60. In order to transpose the signals from the liquid levels 41and 42 from earth coordinates to aircrat coordinates, the liquid levelsignals are resolved in the resolver in terms of the heading of theaircratt in a manner similar to that emplained in the aforementionedPatent 2,591,697. A correction signal representative o the earths rateis connected to another input terminal 0Ef the algebraic summingamplifier 71 in order to correct for the effects oaf the earthsrotational rate on the lquid level 42.

One output terminal of the resolver 60 is connected through an amplitfier 72 and a demodulator 73 to a pitch torquer 74 for applying atorque to the gimbal 25. The other output terminal of the resolver 60 isconnected through a summing amplifier 75 and a demodulator 76 to theroll torquer 77 for applying a torque to the gimbal 29. A signalrepresentative of the true air speed of the craft (TAS -as indicated bythe legend in FIG. 1) is connected to -an input terminal of thealgebraic summing amplifier 75 to correct for the eflect of the cr-aftsvelocity effect-ively in the northerly and easterly directions on theliquid levels 41 and 42 respectively in order that the signals trom theliqud levels 41 and 42 are representative of tilt only neglecting theeects of aircraft acceleration since aircraft acceleration efiects arecompensated for or reduced in a conventional manner known in the artwhich is not shown for purposes of simplicity. 'Ihe resulting precessionof the vertical gyro 24 caused by the signals from the resolver 60provides error signals trom pitch and roll pick-offs and 67,respectively, which are mounted to be responsive to the pitch and rollmovements respectively of the vertic-al gyro 24. The pitch and rollsignals are connected to energize pitch and roll torque motors 6 6 and68, respectively, -for driving the pitch and roll gimbals 20 and 4,respectively, to position the platform 36 in order that the outputs fromthe liquid levels 41 and 42 go to zero.

A synchro transmitter 80 has its rotor positioned in accordance With themovement of the roll gimbal 4 and provides a signal representative ofthe roll of the aircraft to the aircraft flight control or we-aponssystems. A synchro transmitter 81 has its rotor connected to bepositioned in accordance with the movement of the pitch grnbal 20 andprovides a signal representative of the pitch of the craf t to theaircraft flight control or weapon systems.

One of the important features in reducing the drift of both gyroscopes24 and 35 resulting trom unwanted torques, is the use of the principledesoribed in U.S. Patent 2970480, of E. L. Ziegler et al. entitledAnti-Friet-ion Support Meohanism for Gyroscopic Device, issued February7, 1961. As shown in FIGS. 3 to 5, each girnbal is supported bycompoundbearings each having an outer race, a middle race and an innerrace. Rot'aiting the middle race at one end of a gimbal produces torqueson that gimbal by rotating the middle race at the other end of the samegimbal in an opposite direction, torques are created which counteractthose produced by the rotation of the middle race of the firs t hearing.

5. Periodic reversal of the rotation of the middle race of both bearngsaverages the residual torques and produces a very low net torque on thegyro, thereby resulting in a correspondingly low drift rate, whichtheory and structure are more fully described in said U.S. Patent2,970480.

Wi th respect to the vertical gyroscopes 24, a hearing drive motor 85drives the middle races 86, 87, 88, and 89 of the respective compoundbearngs 90, 91, 92 and 93 by means of bevel gears 94, 95, 96 and 97, inthe manner descr-be-d above. With respect to -the azimuth gyroscopes 35,a hearing drive motor 100 drives the middle races 101 and 102 of therespeotive compound bearings 106 and 104 by means of bevel gears 105,106 and 107.

The overall length of the apparatus 1 in the direction of the axis ismade apprecably smaller by means of the large annular roll bearings and11 shown clearly in FIG. 2, which permit a portion of the apparat-us toswing through the opening in the annular roll beanings 10 and1l at highpitch angles as indicated on the dotted lines. The overall height of theapparatus 1 in the direction of the axis 40 is made smaller by mountingthe vertical gyroscope 24 with its pitoh gimbal 25 journ=alled on theouter pitch gimbal 20 inboard r-ather than outboard as is conventionallydone.

It will be noted that the outer ptch gimbal 20 is a panticnlarly ruggedand strong structural member and its transverse pontion is designed tosupport the gyroscopes 24 and 35 in a manner t-hat minimizes theundesirable effects of accelerations acting upon the apparatus 1.

It will be appreoiated that correction signals in addition to thosedescribed above may also be applied in a conventional manner dependingupon the applicat-on for which the gyroscopic apparatus is intended, ina manner well known to those skilled in the art.

While the invention has been described in its preferred em-bodiments, itis to be understood that the words which have been used are words ofdescr-iption rather than limitation and that ohanges wit-hin the purviewof the appended claims may be made without departin-g from the truescope and spirit of the invention in its br-oader aspects.

What is claimecl is:

1. A three axis gyroscopic stable reference apparatus for navigablecraft comprisi-ng,

(1) a first gimbal pivotably supported on said craft for movement aboutthe roll axis of said craft,

(2) a second gimbal pivotably supported on said first gimbal formovement about the pitch axis of said craft,

(3) a pair of gyroscopes pivotably mounted on said second gimbal,

(4) pick-ofr' means connected to said pair of gyroscopes for providingattitude information with re spect to said crait about three mutuallyperpendioular references axes,

(5) at least one of said gyroscopes of said pair being a two degree offreedom gyroscope,

(6) an element pivotably mounted on said second gimbal,

(7) means coupled to said element for stabilizing said element inazimuth,

(8) and means including a pair of acceleration responsive means mountedon said element and hav ing their sensitive axes orthogonally disposedwith respect to each other in a nor-mally horizontal plane for providingsignals representati-ve of the tilt of said azimuth stabilized elementin horizontal, mutually orthogonal directions respectively forstabilizing said first and second gimbals in roll and pitchrespectively.

2. Apparatus of the character described in claim 1 in which at least oneof said gyroscopes is rotatably supported around at least one of itsaxes by means of spaced compound bearings each having an outer race, amiddle race, and an inner race, and means connected to said middle racesfor rotatng said middle races in opposite directions with respect toeach other and periodically reversing the direction of rotation thereof.

3. Apparatus of the character described in claim 1 in which at least oneof the gyroscope of said pair is a single degree of freedorn gyroscopemounted on said azimuth stabilized element for providing directionalgyroscope information.

4. Apparatus of the character described in claim 1 in which said twodegree of freedom gyroscope is mounted directly 011 said second gimbal,and the other gyroscope is a single degree of freedom gyroscope mountedon said azimuth stabilized element for providing azim-uthal referenceinformati-on.

5. Apparatus of the character described in claim 1 in which said twodegree of. freedom gyro is a vertical gyroscope having a rotor and aptch gimbal, said second gimbal beng disposed between said rotor andsaid pitch gimbal, and said pitch gimbal being journalled to said secondgimbal.

6. Apparatus of the character described in claim 1 in which said firstgimbal is pivotably supported about said craft roll axis by means offirst and second spaced circumferential roll bearings at least one ofsaid roll bearings being annular.

7. A three axis gyroscopic stable reference apparatus for navigablecraft comprising,

(1) a first gimbal pivotably supported on said craft for movement aboutthe roll axis of said craft,

(2) a second gimbal pivotably supported on said first gimbal formovement about the pitch axis of said craft,

(3) a two degree of freedom gyroscope pivotably mounted on said secondgimbal,

(4) an element pivotably mounted on said second gimbal,

(5) means coupled to said element for stabilizing said element inazrnuth,

(6) a single degree of reedom gyroscope mounted on said azimuthstabilized element whereby directional gyroscopic properties areimparted thereto for providing an azimuthal signal,

(7) pick-off means connected to said single degree of freedom and twodegree of freedom gyroscopes for providing in combination attitudeinformation with respect to said craft about three mutuallyperpendicular axes,

(8) means including first and second acceleration responsive meansmounted on said element with their sensitive axes orthogonally disposedwith respect to each other in a normally horizontal plane for providingsignals representative of the tilt of said stabilized element inmutually orthogonal directions respectvely for stabilizing said firstand second gimbals in roll and pitch respectively,

(9) each of said gyroscopes being rotatably supported around at leastone of its axis by means of spaced compound bearings each having anouter race, a middle race and an inner race,

(10) and means connected to said middle races for rotating said middleraces of a cooperative pair in opposite directions with respect to eachother and periodically reversing the direction of rotaton of each middlerace.

8. Apparatus of the character described in claim 7 in which said secondgimbal includes a structurally strong central member to which saidgyroscopes are positonably secured on opposite sides thereof.

9. Apparatus of the character described in claim 7 in which said twodegree of freedom gyroscope has an innermost gimbal pivotably mountedfor rotation about the roll aXis of said craft.

10. In a gyroscopic apparatus, for navgable craft, the combinati-onconsisting of (1) a first gimbal pivotably supported on said craft formit said second girnba1 to project partially therethrough movement aboutan axis of said craft, during pivotal rotation thereof.

(2) second gimbal pivotably supported on said first gimbal for movernentabout a second axis of said References Cted by the Exammel craftperpendicular t0 said first axis, 5 UNITED STATES PATENTS (3) agyroscope rotatably supported on sad second 2,729108 v1/1956 vacquier etal glmba 2,936,627 5/1960 Wing et al 745.34

(4) first and second spaced c1rcumferentxal bear1ngs 3,069912 12/1962Faux et 74 5.34

for pivotably mounting said first gimbal about said first axis and atleast one of said circumferential 10 FRED MATTERN Pnmary Examlnel"bearings being annular for ease of maintenance. MILTON KAUFMAN BROUGHTONG. DURHAM, 11. The combination recited in claim 10 in whch the Examners.opening in said annular hearing is sufl'iciently large to per- P. W.SULLIVAN, Assstarzt Examner.

1. A THREE AXIS GYROSCOPIC STABLE REFERENCE APPARATUS FOR NAVIGABLE CRAFT COMPRISING, (1) A FIRST GIMBAL PIVOTABLY SUPPORTED ON SAID CRAFT FOR MOVEMENT ABOUT THE ROLL AXIS OF SAID CRAFT, (2) A SECOND GIMBAL PIVOTALLY SUPPORTED ON SAID FIRST GIMBAL FOR MOVEMENT ABOUT THE PITCH AXIS OF SAID CRAFT, (3) A PAIR OF GYROSCOPES PIVOTABLY MOUNTED ON SAID SECOND GIMBAL, (4) PICK-OFF MEANS CONNECTED TO SAID PAIR OF GYROSCOPES FOR PROVIDING ATTITUDE INFORMATION WITH RESPECT TO SAID CRAFT ABOUT THREE MUTUALLY PERPENDICULAR REFERENCES AXES, (5) AT LEAST ONE OF SAID GYROSCOPES OF SAID PAIR BEING A TWO DEGREE OF FREEDOM GYROSCOPE, (6) AN ELEMENT PIVOTABLY MOUNTED ON SAID SECOND GIMBAL, (7) MEANS COUPLED TO SAID ELEMENT FOR STABILIZING SAID ELEMENT IN AZIMUTH, (8) AND MEANS INCLUDING A PAIR OF ACCELERATION RESPONSIVE MEANS MOUNTED ON SAID ELEMENT AND HAVING THEIR SENSITIVE AXES ORTHOGONALLY DISPOSED WITH RESPECT TO EACH OTHER IN A NORMALLY HORIZONTAL PLANE FOR PROVIDING SIGNALS REPRESENTATIVE OF THE TILT OF SAID AZIMUTH STABILIZED ELEMENT IN HORIZONTAL, MUTUALLY ORTHOGONAL DIRECTIONS RESPECTIVELY FOR STABILIZING SAID FIRST AND SECOND GIMBALS IN ROLL AND PITCH RESPECTIVELY, 